A servicemember may waive any of the rights and protections provided by this Act [sections
of this Appendix]. Any such waiver that applies to an action listed in subsection (b) of this section is effective only if it is in writing and is executed as an instrument separate from the obligation or liability to which it applies. In the case of a waiver that permits an action described in subsection (b), the waiver is effective only if made pursuant to a written agreement of the parties that is executed during or after the servicemember’s period of military service. The written agreement shall specify the legal instrument to which the waiver applies and, if the servicemember is not a party to that instrument, the servicemember concerned.